Fire resistant materials

ABSTRACT

A method for forming a fire resistant material is disclosed. The method comprises providing a plurality of expandable beads of a polymeric material. The beads are coated with an exfoliable graphite. The exfoliable graphite is adhered to the beads with a resin having a solubility parameter of the polymeric material. The beads are thereafter caused or allowed to expand and fuse.

This is a national phase application of International ApplicationPCT/GB03/005204, filed Nov. 27, 2003, and claims priority to UnitedKingdom Patent Application No. 02258722.4, filed Dec. 18, 2002. Thepresent invention concerns the manufacture of fire resistant expandedpolystyrene foams and composite panels constructed from such materials.These foams have a significantly reduced reaction to fire and retain adegree of integrity when exposed to fire regimes. These foams may beproduced entirely within the manufacturing sequences and within the sameequipment as are conventionally and commercially used for the productionof expanded polystyrene (EPS).

Conventionally, expanded polystyrene foam in sheet form is used as aninsulant in building construction and particularly as the core ofinsulating sandwich panels and walls, typically in refrigerationapplications. The skins of such walls or panels are generally thinprecoated steel. The structures may be assembled by the use of adhesivesor mechanical fastenings or a combination of both. EPS sheet is is alsoused as thermal insulation in building construction.

The conventional process for the production of polystyrene foam sheet orforms is as follows:

-   -   (a) Unexpanded polystyrene bead is produced by a suspension        polymerisation process and supplied from the manufacturer in        granular form graded for particle size, the granules being        approximately spherical. This granular polystyrene has a        proportion of pentane dissolved in it which acts as the        expanding or blowing agent.    -   (b) The bead is exposed to heat, usually by steam injected at        the bottom of a tall column. As the beads pass from the bottom        of the column to the top they soften and as the pentane is lost        from solid solution, the released gas causes the softened        polystyrene bead to expand up to fifty times the original        volume. The expanded low density polystyrene bead is collected        at the top of the expansion column.    -   (c) The expanded beads still contain a small amount of pentane        after this primary expansion process. They are wet by virtue of        the steam used in the primary expander and have a partial vacuum        within the pores formed during the expansion in the bead.        Conventionally, the freshly expanded beads are stored in hoppers        and allowed to mature during which process the excess water is        lost and the partial vacuum is equalised to atmospheric        pressure.    -   (d) The matured, expanded beads are introduced into moulds which        have their walls penetrated by many small apertures leading to        plenum chambers behind each wall. The charge may be compressed.        Steam is introduced into the vessel containing the expanded        polystyrene bead at pressures not exceeding 1.5 bar. The        polystyrene beads again soften and the residual pentane is        released. In this second stage the volume expansion of the        charge is contained by the mould walls forcing the beads        together and fusing them to form a single light weight mass of        expanded polystyrene foam.    -   (e) If the mould was in the form of a block, the blocks of        expanded polystyrene are subsequently sliced into sheets, using        hot wires. These slices are used as the cores of the insulating        walls or panels mentioned above.

Polystyrene and exfoliable graphite resin have been previously combinedto produce fire retardant EPS. It is known to incorporate exfoliablegraphite in the initial synthesis procedure (a) above. However, thismethod limits and restricts the methods used in the polystyrene emulsionpolymerisation procedure and process. Satisfactory practice of suchprocedures are subject to significant skill and know how. Incorporationof the additional materials such as exfoliable graphite at this stage isextremely limiting in the practice and flexibility of such processes. Inthis current invention no alteration or modification of the initialsyntheses procedures are required.

The use of exfoliable graphite in applications where it is used to sealgaps in the event of fire is widely taught. The graphite is supported ina binder with or without other inorganic fillers or applied to a textileor felt. These applications are invariably limited to sealing small gapssuch as occur around closures and to sealing, in the event of fire, theresidual openings where penetrations exist around services such as pipesor where cables penetrate what would otherwise be an effective firebarrier installed to provide compartmentalisation.

The use of resin bound exfoliable graphite EPS to provide fire retardantcompositions is also known. The resins disclosed as suitable forexfoliable graphite binders are acrylonitrile/butadiene, styrenebutadiene, ethylene vinyl acetate, polyvinyl acetate, polyvinyl chlorideand polyacrylate resins. These binders act as adequate adhesives for theexfoliable graphite. However, there are adverse effects on the physicalproperties of the polystyrene block and they no additional fireperformance properties.

According to one aspect of this invention, there is provided a method offorming a fire resistant material comprising: providing a plurality ofexpandable beads of a polymeric material; coating said beads with anexfoliable graphite wherein the exfoliable graphite is adhered to thebeads with a resin having a solubility parameter of within substantially0.5 (cal cm⁻³)^(1/2) of the solubility parameter of the polymericmaterial; and thereafter causing or allowing said beads to expand andfuse.

According to another aspect of this invention, there is a fire resistantmaterial comprising: a plurality of expanded and fused beads of apolymeric material, said beads being coated with an exfoliable graphite;and a resin to adhere the exfoliable graphite material to the beads, theresin having a solubility parameter of within substantially 0.5 (calcm⁻³)^(1/2) of the solubility parameter of the polymeric material.

According to another aspect of this invention, there is provided acomposition for forming a fire resistant material comprising a pluralityof expandable beads of a polymeric material, said beads being coatedwith an exfoliable graphite, wherein the exfoliable graphite is adheredto the beads with a resin having a solubility parameter of substantially0.5 (cal cm⁻³)^(1/2) of the solubility parameter of the polymericmaterial.

The polymeric material may comprise polystyrene. Preferably, said beadsare formed into blocks by expansion in closed forms using steam.

The resin may comprise an emulsion comprising one or more of astyrene/acrylic copolymer, a styrene homopolymer, a vinyldene vinylchloride copolymer, methylphenyl siloxane. The resin may include ahalogenated flame retardant and may also include a synergist comprisingan oxide of an element of group 6B of the periodic table. Thehalogenated flame retardant may comprise a brominated flame retardant.The flame retardant may comprise hexabromocyclododecane.

The synergist may comprise tungsten oxide, for example yellow tungstenoxide.

Preferably, the expandable beads comprise partially expanded polystyrenebeads.

According to another aspect of this invention there is provided expandedpolystyrene materials with enhanced fire performance properties producedby coating partially expanded EPS bead with exfoliable graphite using,as the adhesive, resins with a solubility parameter,

of within 0.5 (cal cm⁻³)^(1/2) of polystyrene, these resins being usedas emulsions applied to the expanded polystyrene bead, and the coatedpartially expanded polystyrene bead thereafter being formed into blocksby final expansion in closed forms using steam.

Preferably the resin is an emulsion of a styrene/acrylic copolymer,and/or a styrene homopolymer, and/or a vinylidene vinyl chloridecopolymer and/or methyl phenyl siloxane.

The resin emulsion contains brominated flame retardants and synergistscomposed of oxides of the elements of group 6b of the periodic table

The flame retardant is preferably HBCD.

The synergist may be yellow tungsten oxide.

According to another aspect of this invention, there is provided firebarriers composed of expanded polystyrene materials as described above,assembled between non flammable rigid outer skins where the expandedpolystyrene contains sufficient exfoliable graphite to entirely fill thecavity between the skins left after the melting and loss of thepolystyrene.

In the preferred embodiment of the present invention the above prior artprocess is modified by carrying out one of the following steps after theabove steps (1) to (e), i.e. either:

-   -   (f) coating the unexpanded beads derived from the initial        syntheses with a mixture containing exfoliable graphite and        expanding these beads via the primary expansion process (b)        above; or    -   (g) coating the expanded bead derived from the primary expansion        process (b) above with a mixture containing exfoliable graphite        and after the maturing process (c) above expanding these using        the secondary expansion process into blocks as in (d) above; or    -   (h) coating the matured, expanded beads with a mixture        containing exfoliable graphite and expanding these beads using        the secondary expansion process into blocks as in (d) above.

In (f), (g) and (h) above the exfoliable graphite is caused to adhere tothe bead by incorporating it into a coating mixture of various resinousmaterials. Additionally, other flame retardants and materials acting assynergists to the flame retardant system may be applied to thepolystyrene with the resin and exfoliable graphite mixture.

The exfoliable graphite and resinous material may be compounded togetherand applied to the EPS bead by tumbling the mixture together in a ribbonblender or any other such low shear mixing device. Preferably, theresinous material should be applied to the surface of the EPS bead as itis tumbled in such a mixer, until the surface is evenly coated, and thenthe exfoliable graphite sprinkled onto the tumbling mass and allowed toadhere to the surface of the wet EPS bead.

Exfoliable (or otherwise “expandable”) graphite consists of nativegraphite treated with various acids such as sulphuric, nitric orhydrofluoric such that those additions together with water becomeentrapped between the planes of the graphite crystals at up to 10% ofthe weight of the final product. When such treated graphites are exposedto heat the entrapped materials are released as gas causing the graphiteto expand to up to 250 times its original volume.

The expanded polystyrene beads, modified with the exfoliable graphite asin (e), (f) or (g) above are introduced into the moulds and exposed tothe same steam heating cycle as is described in (c) above. As thepolystyrene beads expand, soften and adhere together, the graphite andresin mixture becomes incorporated into the EPS block. The graphite isentrapped at the boundary of expansion of each bead, but the resin,flame retardants and synergists tend to be entrapped within the EPS.

Beneficial improvements with respect to reaction to fire performance areobtained from additions of graphite equivalent to one tenth the weightof the expanded polystyrene. However, in order to provide the bestreaction to fire performance, or the most stable fire protection, theweight of exfoliable graphite needs to be approximately equivalent tothe weight of polystyrene and, hence, doubles the density of the EPS.Given that EPS is used primarily for its thermal insulation properties,the doubling of the SG does not significantly alter the insulationproperties of the modified EPS.

When the modified polystyrene produced as above is exposed to heat andfire regimes an entirely different behaviour is observed in comparisonwith unmodified expanded polystyrene. If exposed directly to a fireregime, the exfoliable graphite activates and intumesces outwards towardthe heat source producing a largely inflammable insulating massprotecting the underlying EPS. The character and rigidity of thecarbonaceous char can be critically modified by selection of the resinin the resin mixture.

Further, in the presence of the intumescent mass the effectiveness ofthe additional flame retardant systems appear enhanced in terms of thereduction in the combustion of volatile gases and smoke emission. Underfire conditions unmodified EPS will produce flaming droplets of moltenEPS from the fire zone. While conventional flame retardants can causethe flaming droplets to extinguish quite quickly, the methods andprocedures revealed in this current invention can eliminate thisphenomenon

Further, if the expanded polystyrene so modified with exfoliablegraphite and selected resins is constructed into composites with fireresistant skins composed of steel, phenolic laminate or ceramic board,then such composite structures will act as thermally insulatingbarriers, which in the event of a fire regime will act as fire barriers.In this situation the behaviour of the exfoliable graphite modified EPSwill be different from its behaviour when exposed directly to flame.Exposed to a fire regime such as that defined in EN 1363, the exfoliablegraphite will expand to entirely fill the void between the skinspreviously occupied by the exfoliable graphite modified EPS with astable graphitic char mass that will act as a stable insulation capableof a fire protection rating for the composites of up to one hour. If themodified EPS is intended for such fire protection applications then theselection of the grade of exfoliable graphite is critical and its levelof incorporation must be selected to entirely fill the residual cavitybetween the skins of the walling system.

It should be appreciated that the resin binder used will have asignificant effect on the physical properties of the exfoliable graphitemodified EPS. One aspect of the preferred embodiment of the presentinvention is the nature of the resin binder system used. It is anadvantage of the preferred embodiment that the physical properties ofthe EPS are either improved or unaltered while gaining the advantages infire and flame performance. In the preferred embodiment, the resinmixture is applied to the outside of the beads, and appears as a film onthe outside of the beads. In the final expansion procedure of thepreferred embodiment the beads expand into and through this film andfuse together to form the finished blocks. Hence, the residue of theapplied resin film will appear at the cell junctions. Unless the appliedresin is compatible with the polystyrene the final block will beweakened.

The compatibility of the binder resins may be determined byconsideration of the solubility parameters of the binder resin and thepolystyrene. Generally for mutual solubility, the solubility parameter,

of the two resins must be within 0.5 (cal cm⁻³)^(1/2). In the preferredembodiment of the present invention, the resin latexes used as graphitebinders to the beads are styrene/acrylics and/or, polyvinylchloride/poly vinylidene copolymers and/or styrene homopolymers and/ormethylphenyl siloxanes, which may be all applied in emulsion form

Another aspect of the preferred embodiment is the incorporation ofsynergists to the flame retardant system. Brominated flame retardants,particularly hexabromocyclododecane (HBCD), have conventionally, beenincorporated into EPS to improve flame retardancy. Metal oxides,preferably of group 6B of the periodic table, may be provided to act assynergists to the flame retardant. Significant further reduction onsmoke emission and a reduction of flammability is observed if the metaloxides are added to the mixture applied to the EPS bead with the resinand/or exfoliable graphite system. As in EP 01309918.9 tungsten oxide isthe preferred synergist.

Embodiments of the invention will now be disclosed, by way of exampleonly.

All the below examples illustrating the method and effectiveness of theprocess, use one of the two routines as follows.

A) Application to Freshly Expanded EPS Bead.

Polystyrene bead expanded in the conventional manner from the primaryexpander, is coated with a mixture of the selected latexes withadditional flame retardants and synergist. For convenience, the beadshould be taken and treated directly from the primary expander. Themanner of application is irrelevant providing that the beads areagitated or stirred so as to properly and completely coat the surface ofthe bead. A conventional ribbon blender or any apparatus with similarlyeffective action is suitable. When the bead is fully coated theexfoliable graphite is sprinkled onto the surface of the bead anddistributed in a similar manner. The resinous latex will cause theexfoliable graphite to adhere to the surface of the bead. The bead isthen allowed to dry and mature as is conventional, preferably inventilated textile bags. When dry the bead behaves no differently fromuncoated bead and therefore may be handled by conventional systemscommon to the art. The bead is loaded into the block or form moulds, andexpanded with steam to form rigid shapes or blocks

B) Application to Matured EPS Bead.

Polystyrene bead, expanded in the conventional manner from the primaryexpander and matured in ventilated textile bags, is coated with amixture of the selected latexes with additional flame retardants andsynergist. When the bead is fully coated the exfoliable graphite issprinkled onto the surface of the bead and distributed in a similarmanner. The bead is then loaded directly into the block moulds. In spiteof being wet, the bead behaves in a similar manner to uncoated bead.However, because the bead is wet with the water from the resin emulsionand any additional water used, extended steaming times are required tofully set the block and the EPS blocks so formed require up to 14 daysfor their weight to stabilise.

Subsequent to either procedure above, the blocks may be cut with hotwire cutters in the same manner as unmodified EPS blocks.

The invention may be illustrated by the following 22 examples, theformulations, procedures and results are shown in tables 1, 2 and 3below.

The examples were produced in a laboratory block mould 200×200×300 mmsimulating the behaviour and construction of full scale production blockmoulds. Examples 1 to 12 were produced by taking matured bead, coatingthem with the resin mixtures, flame retardants and synergist as shown,subsequently coating the dampened surface with exfoliable graphite andthen expanding them while still wet in the block mould with steamapplied to the block mould at 102 to 111° C. at between 1.5 and 2.5 Bar.

Examples 13 to 22 were produced by taking freshly expanded bead, coatingthem with the resin mixtures, flame retardants and synergist as shown,and subsequently coating the dampened surface with exfoliable graphite.The beads were then matured in textile bags and then expanded dry in thelaboratory block mould with steam applied to the block mould at 102 to111° C. at between 1.5 and 2.5 Bar

In the examples styrene acrylic resins are represented by Pliolite LS1 aproduct of Goodyear Chemicals, polystyrene resins are represented byEmultex 340 a product of Synthomer Ltd, vinyl/vinylidene chloride resinsare represented by Haloflex 202 a product of Neoresins BV and phenylmethyl siloxanes are represented by Silikophen P65W a product of ThomasGoldshmidt GmBH.

The additional flame retardant is HBCD (hexabromocylcododecane) but maybe any conventional brominated flame retardant. The synergist istungsten oxide but may be any oxide or combination of oxides fromelements of group 6b of the periodic table. It will be noted thatexample 22 is a control.

The fire protection performance was measured by assembling 200×200×100mm specimens cut from the blocks made in the laboratory block mould,between 0.8 mm thick plastisol coated steel skins and mounting them asfire barriers in a test furnace capable of reproducing the ISOcellulosic fire curve. The back face temperature of the specimens wasmonitored to failure temperature of an average of 140° C. above ambient.After firing the cold face of each specimen was removed and the stateand condition of the exfoliable graphite char recorded, particularly theability of the char to fill the cavity previously occupied by themodified EPS.

The reaction to fire performance was measured by assembling two600×100×50 specimens cut from the blocks made in the laboratory blockmould in an apparatus capable of simulating the conditions of the SingleBurning Item apparatus (EN 13823). This apparatus has been shown to havea correlation of 0.93 between the Fire Growth Rate Index (FIGRA) itrecords and the FIGRA as recorded by the full scale apparatus.Therefore, by calculation an indicated Euroclass was calculated.

The measurement of the physical properties was entirely conventional.

It is quite clear from the shown results that with the defined resintypes:

-   -   (a) providing sufficient exfoliable graphite is present in the        formulation to fill the cavity left between the skins of the        fire barrier upon ignition excellent fire barriers can be        achieved with no loss of low temperature insulation.    -   (b) excellent reaction to fire properties are achievable for        exposed EPS with an improvement in physical properties.    -   (c) additional conventional flame retardants and their        synergists may be advantageously included in the mixtures        applied to the EPS.

TABLE 1 Experimental Weight of charges to a 200 × 200 × 300 mmLaboratory Scale Block Mould Example No Condition EPS Bead Wt EPS WtGraphite Resin Wt Resin Water HBCD WO2 1 WAWS 1420 F 330 330 PlioliteLS1 110 110 2 WAWS 1420 F 330 330 Emultex 340 110 110 3 WAWS 1420 F 330330 Emultex 340 110 0 3.3 4 WAWS 1420 F 330 330 Emultex 340 110 110 3.33.3 5 WAWS 1420 F 330 330 Haloflex 202 110 0 6 WAWS 1420 F 330 330Haloflex 202 110 55 3.3 7 WAWS 1420 F 330 330 Haloflex 202 110 55 3.33.3 8 WAWS 1420 F 330 330 Silikophen P65W 110 55 9 WAWS 1420 F 330 330Silikophen P65W 110 55 3.3 3.3 10 WAWS 1420 F 330 330 Haloflex 202 55 0Silikophen P65W 55 11 WAWS 1420 F 330 330 Haloflex 202 55 110 3.3Silikophen P65W 55 12 WAWS 1420 F 330 330 Haloflex 202 55 55 3.3 3.3Silikophen P65W 55 13 WADS 1014 F 330 330 Pliolite LS1 110 110 — 14 WADS1014 F 330 370 Pliolite LS1 110 110 — 15 WADS 1014 F 330 370 PlioliteLS1 110 110 — 16 WADS 1014 F 330 370 Pliolite LS1 110 110 2.5 17 WADS1014 F 330 370 Haloflex 202 110 55 6 3 18 WADS 1014 F 330 370 Haloflex202 110 55 19 WADS 1014 F 330 370 Haloflex 202 110 55 2.5 20 WADS 1014 F330 370 Haloflex 202 110 55 6 3 21 WADS 1014 F 330 370 Haloflex 202 1106 3 Silikophen P65W 110 22 WADS 1014 F 330 — nil — — — — KEYWAWS—matured bead, Wet Applied Wet Steamed WADS—freshly expanded bead,Wet Applied, matured, Dry Streamed

TABLE 2 Examples 1 to 22 formulation weights by percentage % Graph- %Resin To- % EPS ite Solids % HBCD % WO2 tal example 1 46.88 46.88 6.25 00 100 example 2 46.15 46.15 7.69 0 0 100 example 3 45.94 45.94 7.66 0.460 100 example 4 45.73 45.73 7.62 0.46 0.46 100 example 5 46.15 46.157.69 0 0 100 example 6 45.94 45.94 7.66 0 0.46 100 example 7 45.73 45.737.62 0.46 0.46 100 example 8 46.88 46.88 6.25 0 0 100 example 9 46.4446.44 6.19 0.46 0.46 100 example 10 46.51 46.51 6.98 0 0 100 example 1146.3 46.3 6.94 0.46 0 100 example 12 46.08 46.08 6.91 0.46 0.46 100example 13 46.88 46.88 6.25 0 0 100 example 14 44.35 49.73 5.91 0 0 100example 15 44.35 49.73 5.91 0 0 100 example 16 44.21 49.56 5.89 0.33 0100 example 17 43.19 48.43 7.2 0.79 0.39 100 example 18 43.71 49.01 7.280 0 100 example 19 43.56 48.84 7.26 0.33 0 100 example 20 43.19 48.437.2 0.79 0.39 100 example 21 43.19 48.43 7.2 0.79 0.39 100 example 22100 100

TABLE 3 Performance Results for Examples 1 to 22 Fire Protection ResultsPhysical Properties Time to Temp. at Temp. at Reaction To Fire ResultsCrush K Value □140 30 Mins 60 Mins % Fill of FIGRA Calculated EuroclassStrength 50% J M⁻¹K⁻¹ Example Minutes Deg C. Deg C. Cavity (PD) FIGRAEstimated SG 75% Pascal Pascal 10² example 1 39.5 118 90 41.04 4.72 D 2811,300 18,200 example 2 12.5 334 60 47.77 5.52 D 25 12,800 20,400example 3 11 330 50 20.02 2.21 D 25 11,800 19,700 example 4 10.5 293 3522.69 2.53 D 31 13,200 20,400 example 5 13.5 239 75 20.27 2.24 D 3411,700 17,900 example 6 10 312 65 32.19 3.66 D 31 14,600 22,600 example7 12 223 60 23.68 2.65 D 35 13,400 21,000 example 8 8 369 40 6.41 0.58 C33 example 9 11.5 302 50 4.72 0.38 B 18 13,500 20,800 example 10 9.5 33470 7.2 0.68 C 38 11,200 18,200 example 11 13 202 75 9.64 0.97 C 3212,100 19,600 example 12 9 384 25 21.05 2.33 D 33 11,100 18,200 example13 33.5 149 220 80 45.43 5.24 D 29 18,200 24,000 39.2 example 14 >70 82141 100 37 4.24 D 28 13,000 25,700 48.5 example 15 49 110 173 100 26.913.03 D 31 12,600 24,400 39.2 example 16 29.5 162 186 90 41.43 4.77 D 2816,800 31,300 43.5 example 17 40.5 128 189 85 6.68 0.61 C 33 16,80029,400 57.3 example 18 49 117 173 85 38.68 4.44 D 35 16,500 27,300 42.7example 19 58 101 162 90 22.8 2.54 D 31 11,900 24,700 39.2 example20 >70 80.3 143 95 4.69 0.38 B 35 12,700 25,400 42.1 example 21 >70 83.8121 95 3.4 0.22 B 35 14,000 25,100 33 example 22 7 418 519 0 111.3913.13 E 17 10,000 22,900 30.3

1. A composition for forming a fire resistant material comprising aplurality of expandable beads of a polymeric material, wherein thepolymeric material comprises polystyrene, said beads being coated withan exfoliable graphite, characterised in that the exfoliable graphite isadhered to the beads with a resin comprising an emulsion comprising astyrene homopolymer, the resin having a solubility parameter of withinsubstantially 0.5 (cal cm⁻³)^(1/2) of the solubility parameter of thepolymeric material.
 2. A composition according to claim 1 characterisedin that the resin comprises an emulsion further comprising one or moreof a styrene/acrylic copolymer, a vinylidene vinyl chloride copolymer,and methylphenyl siloxane.
 3. A composition according to claim 1characterised in that the resin includes a halogenated flame retardant.4. A composition according to claim 3 characterised in that the resinincludes a synergist comprising an oxide of an element of Group 6B ofthe Periodic Table.
 5. A composition according to claim 3 characterisedin that the halogenated flame retardant comprises a brominated flameretardant.
 6. A composition according to claim 3 characterised in thatthe flame retardant comprises hexabromocyclododecane.
 7. A compositionaccording to claim 4 characterised in that the synergist comprisestungsten oxide.
 8. A composition according to claim 4 characterised inthat the synergist comprises yellow tungsten oxide.
 9. A compositionaccording to claim 1 characterised in that the expandable beads comprisepartially expanded polystyrene beads.
 10. A fire resistant materialcomprising a composition according to claim 1 wherein the beads havebeen allowed to expand and fuse together.
 11. A fire carrier formed of afire resistant material according to claim 10 arranged betweennon-flammable outer skins where the fire resistant material containssufficient exfoilable graphite substantially to fill the cavity betweenthe skins on expansion thereof after melting and loss of withinsubstantially 0.5 (cal cm⁻³)^(1/2) of the polymeric material in a firesituation.
 12. A method of forming a fire resistant material comprising:providing partially expanded polystyrene beads; coating the partiallyexpanded polystyrene beads with exfoliable graphite using, as anadhesive, a resin comprising an emulsion comprising a styrenehomopolymer, the resin having a solubility parameter of withinsubstantially 0.5 (cal cm⁻³)^(1/2) of the solubility parameter of thepolystyrene beads; and forming the coated partially expanded polystyrenebeads into blocks by a final expansion in closed form using steam.